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Updated: Jul 13, 2026
Isolation and Characterization of a Head and Neck Squamous Cell Carcinoma Subpopulation Having Stem Cell Characteristics
Published on: May 11, 2016
Downregulation of RAD17 in head and neck cancer
Ming Zhao1, Shahnaz Begum, Patrick K Ha
1Department of Otolaryngology-Head and Neck Surgery, Head and Neck Cancer Research Division, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
Background:
DNA repair genes play a critical role in maintaining genome stability and have been implicated in tumorigenesis. Head and neck squamous cell carcinoma (HNSCC) often shows chromosomal instability. We examined the expression of human RAD17, a DNA damage cell cycle checkpoint gene, in primary head and neck cancer tissue.
Methods:
Significance analysis of microarrays was applied to expression array results examining more than 12,000 genes in 7 samples of primary HNSCC and 6 samples of normal control oral epithelial tissue. Additional confirmation was performed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) in these samples and western blot with an additional 12 primary HNSCC and 7 normal samples, followed by loss of heterozygosity (LOH) analysis and quantitative PCR at the RAD17 locus.
Results:
Multiple checkpoint and DNA repair genes were downregulated in primary head and neck tumor tissue compared with normal control epithelial tissue, including hRAD17. Its Z-score and fold change were -2.5 and 0.39, respectively. The results of normalized, quantitative RT-PCR showed decreased expression of hRAD17 mRNA in tumor tissue (mean value 0.2166) when compared with normal tissue (mean value 0.3957, p < .05). Western blot demonstrated undetectable expression of hRAD17 protein in primary tumor tissue (0/12), while there was strong expression of hRAD17 protein in normal oral mucosal tissue (6/7). To determine possible mechanisms of inactivation, the hRAD17 locus at 5q13 was analyzed using microsatellite markers, showing 70% LOH in 30 primary HNSCCs. Quantitative PCR showed that RAD17 DNA copy number was decreased in the majority of head and neck tumor tissue samples.
Conclusion:
Loss of hRAD17 expression occurs frequently in HNSCC, is often due to genomic deletion, and may facilitate genomic instability in HNSCC.
Insights
Loss of the RAD17 gene expression is frequent in head and neck squamous cell carcinoma (HNSCC). This downregulation, often due to genomic deletion, may contribute to genomic instability in HNSCC.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- DNA repair genes are crucial for genome stability and implicated in cancer development.
- Head and neck squamous cell carcinoma (HNSCC) frequently exhibits chromosomal instability.
- The study investigates the expression of human RAD17, a DNA damage cell cycle checkpoint gene, in HNSCC.
Purpose of the Study:
- To examine the expression levels of the human RAD17 gene in primary HNSCC tissues.
- To investigate potential mechanisms underlying RAD17 alterations in HNSCC.
- To assess the correlation between RAD17 expression and genomic instability in HNSCC.
Main Methods:
- Utilized Significance Analysis of Microarrays (SAM) on gene expression data from HNSCC and normal tissues.
- Confirmed hRAD17 expression using quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot.
- Analyzed RAD17 locus for loss of heterozygosity (LOH) and DNA copy number variations via quantitative PCR.
Main Results:
- Multiple DNA repair and checkpoint genes, including hRAD17, were found to be downregulated in HNSCC.
- Quantitative RT-PCR revealed significantly decreased hRAD17 mRNA levels in tumor tissues compared to normal tissues (p < .05).
- Western blot showed undetectable hRAD17 protein in most HNSCC samples (0/12), contrasting with strong expression in normal tissues (6/7).
- Analysis indicated frequent loss of heterozygosity (70%) and decreased DNA copy number of RAD17 in HNSCC samples.
Conclusions:
- Loss of hRAD17 expression is a common event in HNSCC.
- Genomic deletion is a frequent mechanism leading to RAD17 inactivation in HNSCC.
- Reduced hRAD17 expression may contribute to the genomic instability observed in HNSCC.
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